THE DISTRIBUTION OF THE ELEMENTS IN IGNEOUS 
. ~ ROCKS.¢ 
By Henry S. WASHINGTON, New York, N. Y. 
(Chattanooga meeting, October, 1908.) 
I, INTRODUCTION. 
During the last twenty years or so the chemical investigation of 
rocks has made great advances, and it is now generally recognized 
that a knowledge of the chemical composition is as essential as that 
of the texture or mineral composition, if not more so, for the proper 
classification of rocks and study of their origin and relationships. 
Rock analyses have vastly increased in numbers and, what is of 
greater importance, in quality. New and improved methods permit 
of greater accuracy than was possible in the early days, and the list 
of chemical constituents frequently determined has risen from the 
seven or eight of the greater part of the nineteenth century to twenty 
or more. Indeed, rock analyses with determinations of so many con- 
stitutents are now commonly made by the chemists of the United 
States and Australia, while in Germany, Great Britain, France, and 
Italy the rarer constituents are determined more frequently than 
formerly. 
As a consequence of this modern, accurate work, it has been dis- 
covered that some elements which were formerly supposed to be rare 
are of widespread occurrence and are often present in considerable 
amount. The fact is further being developed that the elements tend 
to show certain relations of occurrence or abundance in connection 
with each other. This is a fact which is applicable to the rarer ele- 
ments, and which also finds a broad geological and _petrological 
expression in the recognition of petrographic provinces. We are 
beginning to obtain some definite, though as yet rudimentary, knowl- 
edge of the distribution of the elements among igneous rocks. 
@ Reprinted by permission from Bi-Monthly Bulletin of the American Institute 
of Mining Engineers, New York, No. 23, September, 1908, pp. 809-838; also in 
Transactions, pp. 735-764. 
45745°—sm 1909——19 279 
